The object of the proposed research is to assist in the development of new anti-cancer drugs by the isolation and structure determination of active antitumor agents from plants. The tumor inhibitors of the two plants Tobernaemontana johnstonii and T. usambarensis and at least two other plants will be isolated by a combination of systematic fractionation procedures with one or more of the specific bioassay systems developed by the Drug Research and Development Branch of the National Cancer Institute. The isolated tumor inhibitors will be identified by comparison of their physical and spectroscopic properties with those of known compounds, and the structures of new compounds will be elucidated by modern physical techniques including, in appropriate cases, single-crystal X-ray structure determination. For compounds showing significant in vivo activity, a detailed methodology will be worked out for extraction of the compounds on a large scale for extensive pharmacological testing.